1. Field of the Invention
This invention relates to a yarn tension device for applying a tension to a moving yarn supplied to a knitting or weaving apparatus such as a knitting machine, a loom or the like.
2. Related Art
Conventionally, in a knitting machine for knitting socks, sweaters or the like, numerous yarns are severally supplied to the knitting machine through yarn tension devices.
A conventional yarn tension device includes a receiving plate and a pushing plate for clamping a moving yarn, a spring for urging the pushing plate toward the receiving plate and an adjusting means for adjusting the elastic force of the spring. The moving yarn is clamped between the receiving plate and the pushing plate and a predetermined tension is applied thereto by the adjusting means.
In the conventional yarn tension device described above, the moving yarn passes between the receiving plate and the pushing plate. Therefore, yarn dust such as lint adheres to the contacting surfaces of the receiving plate and the pushing plate. Further, for example, with yarn for knitting socks coated by a wax, when the moving yarn passes between the moving plate and the pushing plate and frictionally rubs thereagainst, wax adheres to the contacting surfaces.
Wax adheres to the contacting surfaces and gradually accumulates, disturbing the smooth moving of the yarn. Moreover, under this condition, a tension which is larger than the predetermined tension is applied to the yarn. As a result, this phenomenon leads to the yarn breaking or yarn disarrangement of the sock to be knitted. Further, in this condition, when a front yarn and a rear yarn are knitted, there is a danger of the surface yarn and the back yarn being reversely knitted (defective plating).
Therefore, in conventional devices, frequent maintenance is required to clean the contact surfaces of the receiving plate and the pushing plate.
However, because the knitting or weaving machine receives numerous yarn and the number of yarn devices is the same as the number of yarns, when a cleaning operation is carried out on all the yarn tension devices, a lot of work and a long time are required. Further, the knitting machine must be stopped during the cleaning operation, and productivity is deteriorated.